Microwave-Assisted Post-processing of Detonation Gun-Sprayed Coatings for Better Slurry and Cavitation Erosion Resistanc
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Microwave-Assisted Post-processing of Detonation Gun-Sprayed Coatings for Better Slurry and Cavitation Erosion Resistance Abhishek Babu1 • H. S. Arora1 • H. S. Grewal1
Submitted: 1 May 2019 / in revised form: 8 August 2019 ASM International 2019
Abstract Slurry and cavitation erosion often limits the durability of many fluid machines such as hydroturbines, pumps, and propellers. Despite good resistance against slurry erosion, thermal spray coatings generally exhibit poor resistance against cavitation erosion. The performance of thermal spray coatings under cavitation erosion is limited by the presence of defects such as pores, splat boundaries, and limited adhesion with the substrate. In the present work, we performed post-processing of the WC10Co-4Cr and Ni coatings deposited using the detonation gun process. For post-processing, microwave technique was used owing to its capability for atomic-level heating. The microstructural characterization of the as-sprayed and post-processed coatings showed significant homogenization for the latter. Compared to the typical lamellar structure of as-sprayed, the processed samples exhibited a columnar structure with metallurgical bonding with the substrate. The mechanical properties of the coatings were significantly improved after post-processing owing to the elimination of splat boundaries and pores which significantly enhanced the cavitation and slurry erosion resistance. Post-processed coatings showed at least ten times higher resistance to cavitation erosion. The slurry erosion resistance of the coatings also improved up to three times depending upon the impingement angle. A significant difference in the erosion mechanism was also observed after post-processing.
& H. S. Grewal [email protected] 1
Surface Science and Tribology Lab, Department of Mechanical Engineering, Shiv Nadar University, Gautam Budh Nagar, India
Keywords cavitation erosion detonation gun spraying slurry erosion
Introduction Slurry and cavitation erosion is a severe concern for hydraulic components, mining, utility, and oil refinery sectors. The adverse working conditions in these sectors cause significant degradation of the components. Surface modification techniques provide a viable and cost-effective solution for addressing the deterioration results from erosive wear. Many prior studies have reported the use of thermally sprayed coatings for protection against such deleterious environments (Ref 1-3). Owing to extremely high hardness, good corrosion resistance, and moderate fracture toughness, WC-based cermet coatings have been effectively used for countering slurry erosion–corrosionresistant surfaces (Ref 4-7). Among different thermal spray processes, high-velocity oxy-fuel (HVOF) and detonation gun (D-gun) techniques have been extensively used for forming hard cermet coatings. These techniques are preferred over flame and plasma spray processes due to their ability to form dense coatings along with good adhesion with the substrate (Ref 8). Among the various WC-based
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